* Magnitude is how bright a star appears from Earth.

* Size is the actual physical diameter of a star.

Here's the breakdown of how the Greek letter designations work:

* Alpha (α) is assigned to the brightest star in a constellation.

* Beta (β) is the second brightest, and so on.

However, brightness doesn't always correlate with size. A star can be very large but faint if it's far away. Conversely, a small star can be incredibly bright if it's very hot and close to us.

To answer your question about size, we need more information. You'd need to specify the constellation you're interested in, and then we could compare the actual sizes of the alpha, beta, gamma, and delta stars within that constellation.